The invention pertains generally to special feature arrangements for electronic private automatic branch exchanges and more particularly to a local transfer arrangement for an EPABX which is built around a space-divided rectangular switching matrix.
Normally, the feature of local transfer is provided by an equipment configuration capable of allowing one local station (hereinafter termed the transferring station) to forward another connected local station (hereinafter termed the transferred station) to a third local station (hereinafter termed the transferee station). The local transfer feature permits the transferred station to be connected to the transferee station without re-dialing by the transferred station.
Typically, the local transfer function is provided as a common feature on many key systems where a manual pushbutton or the like controls circuitry for the local transfer operation. This method requires additional equipment to be added to the system and another signaling devices that must be operated by the subscriber. Further, local transfer between private automatic branch exchange stations not using key systems is usually not available or must be attendant assisted.
Some private automatic branch exchanges which include key system features provide for marking line and junctor appearances on either side of a switching matrix and path finding between appearances by way of a free mark lead. The path through the switching matrix is generally held by energizing a sleeve lead along the free path found. The sleeve lead must remain energized throughout the process of local transfer since if any part of the connection is broken, the held party (transferred party) will be released.
Recently, an electronic private automatic branch exchange which is built around a space divided rectangular solid state switching matrix was developed to provide an exchange which is more dependable in operation and less subject to misoperation due to interference, cross-talk and other problems.
In this exchange one side of the solid state matrix provides line appearances which are connected to line circuits, tone receivers, senders and operator loops. The other coordinate side of the matrix provides junctor appearances for connection to an attendant junctor, local junctor and trunk junctors. The solid state switching matrix is a single stage matrix providing direct connection between line appearances and junctor appearances by the closing of a single crosspoint, and connection between lines within the system is effected simply by the interconnection of a pair of crosspoints associated with the respective lines and a selected junctor, thereby providing a greatly decreased amount of switching for establishing a connection through the matrix.
The matrix in this electronic PABX is employed only for providing an audio path between stations and junctors and is, therefore, not advantageously connectable with many prior art local transfer arrangements using a sleeve lead for path finding.
The electronic private automatic branch exchange providing the above features is more fully described in copending application, entitled, "Electronic Private Automatic Branch Exchange," Ser. No. 431,928, filed on Jan. 9, 1974, in the names of Uwe A. Pommerening and Glenn L. Richards, assigned to the same assignee as the present application, and the disclosure of which is incorporated herein by reference.
The control system for the matrix of the above-referenced exchange is more fully described in a copending application, entitled, "Matrix Control For Electronic Private Automatic Branch Exchange," Ser. No. 431,878, filed on Jan. 9, 1974, in the names of Uwe A. Pommerening and Glenn L. Richards, assigned to the same assignee as the present invention, and the disclosure of which is incorporated herein by reference.
A tone control arrangement for the above referenced exchange is more fully described in a copending application, entitled, "Tone Control For Electronic Private Automatic Branch Exchange," Ser. No. 431,885, filed on Jan. 9, 1974, in the names of Glenn L. Richards and Uwe A. Pommerening, assigned to the same assignee as the present invention, and the disclosure of which is incorporated herein by reference.